Theoretical study of the protolytic dissociation of HCl in water clusters

Reaction mechanisms for the acidic dissociation of HCl in water clusters ar e considered. Intermediates in the reaction are obtained from stationary po ints on the potential energy surface of the systems HCl-(H2O)(n) with n=4 a nd 5. These points have been determined by the B3LYP density functional met hod in an aug-cc-pVDZ atomic orbital (AO) basis. The total energies of the stationary points are checked by the coupled cluster single-double-triple [ CCSD(T)] method in the same AO basis. For the case of n=4 a multibody analy sis of the interaction energies is performed by the CCSD(T) method as well as by symmetry adapted perturbation theory. The clusters have a completely dissociated form as their energetically lowest minimum. (C) 2001 American I nstitute of Physics.